Palladian windows: Despite the popularity of this type of window (a large center window topped by an arched window and flanked by two side panels), designers agree that Palladian windows are one of their biggest challenges.

If the window cannot be left uncovered, curtains can be hung above the arch. The consensus is that the rod should not be hung at the bottom of the arch because that bisects the window.

Another option for arched windows is to hang a soft shade or swag that follows the curve, with matching shades on the adjacent windows. Thomas Jayne suggests using a curtain similar in color to the walls so it blends in rather than calls attention to itself.

French doors: Curtains should completely clear the doors so they can open. Or mount Roman shades onto each door. Thomas Jayne once designed flat panels with buttonholes that attached to small brass cleats.

If a wall or room is lined with pairs of French doors, consider running a rod all the way across the wall, or a track all the way around the room, and flanking each set of doors with curtains. "What you don't want to do is have one long valance and one set of curtains for multiple sets of French doors," says Cathy Kincaid.

Bay or bow windows: Bay windows are often best addressed with shutters or soft fabric shades. Another option is to hang floor-length curtains on each side, and possibly run a cornice or valance across the top of the window. Custom curtain tracks can be curved or angled to match a bay or bow window.